A direct ultratrace determination of platinum in environmental, food and biological samples by ICP-SFMS using a desolvation system

Abstract

The purpose of this study was to develop a robust, reliable and accurate method that allows measurements of platinum in the sub-ppt range in environmental, food and biological samples. The quantification of platinum was performed with digested samples, exploiting the high sensitivity of inductively coupled plasma sector field mass spectrometry (ICP-SFMS) in low resolution mode. The hafnium oxide interference affecting the determination of platinum was investigated. A desolvation device in combination with a membrane unit was used as the sample introduction system, in order to minimize the oxide formation. A HfO⁺/Hf⁺ ratio of 0.01% was obtained (50 times lower than with a standard inlet system), thus interferences were strongly reduced and no mathematical corrections were necessary in most samples. The platinum value found in the reference material road dust BCR 723 agreed with the certified value (within the 95% confidence limit). Additionally, recovery tests in spiked peat and hay samples confirmed the accuracy of this technique at an acceptable precision from 3.5% to 15.5% (RSD). The method was applied to the measurement of environmental and food samples from two locations, one near a well-frequented motorway, one from an alpine site. The higher platinum concentrations measured at the first site confirmed the polluting effect of the traffic. Swiss diet samples, urine samples and corresponding reference materials, SRM 1548 and SRM 2670 for total diet and urine, respectively, were measured as well. The method was successfully applied to the determination of trace and ultratrace levels of platinum in the samples, with very low limits of detection of 4.5 ng kg⁻¹ in dry environmental and food samples, corresponding to 0.2–1.8 ng kg⁻¹ in fresh weight samples and of 0.5 ng L⁻¹ in urine samples.